1. Field of the Invention
The invention relates to an elastomeric vehicle launching system, and more particularly to a low noise, low volume, low elastomeric strain impulse fluid delivery apparatus of concentric elastomeric rings.
2. Description of the Prior Art
Impulse fluid flows are used to launch vehicles from submarine platforms. Launch systems in the prior art include the single stroke reciprocating pump, and the rotary air turbine pump. Additionally, elastomeric ejection systems have been developed, which store impulse fluid in charged el-astomeric bladders.
The single stroke reciprocating pump converts pneumatic potential energy from compressed air stored in a flask into working fluid kinetic energy. The pump utilizes a massive piston apparatus to transfer sufficient working fluid, such as seawater, to launch a projectile. The system has proven reliable, but has significant disadvantages. Its complexity results in high system and maintenance cost, and the rapid conversion of pneumatic potential energy into the vehicle kinetic energy results in significant radiated noise.
The air rotary turbine pump also converts potential energy in the form of compressed air stored in a flask into kinetic energy of a working fluid. An air turbine drive unit is joined with a rotary impeller pump via a speed reduction unit. This system suffers from disadvantages similar to those of the single stroke reciprocating pump. An alternative type of launch system is the elastomeric ejection system (EES) which addresses the problems of the single stroke reciprocating pump and the air rotary turbine pump. U.S. Pat. No. 4,848,210 discloses a n elastomeric impulse energy storage and transfer system. The system of this patent is adapted to a torpedo launch system wherein an elastomeric bladder is distended by filling it with pressurized fluid. When a fluid impulse is desired, the elastomeric bladder discharges its volume of working fluid to eject a projectile from the launch system into the surrounding liquid. The elastomeric bladder used is generally spherical, containing an expanded volume sufficient to fill the launch tube and the launch way forward of the launch tube.
U.S. Pat. No. 5,200,572 discloses an EES bladder, which has an elevation of frusto-ellipsoidal configuration and an ellipsoidal sectional plane parallel to the base of the bladder. The bladder of this patent is aimed at achieving a smooth and even flow of impulse fluid from the bladder to further reduce radiated noise.
U.S. Pat. No. 5,231,241 further discloses an EES configuration in which a submarine hull partially defines the volume of fluid stored in the elastomeric bladder. An impulse tank is defined by the volume between the inner hull and an elastomeric sheet. Pressurized liquid causes the diaphragm to expand within the outer hull to generate the required potential energy for a launch. U.S. Pat. No. 5,231,241 is hereby incorporated by reference.
The above EES systems suffer from cavitation noise following launch. When the finite volume of fluid in the bladder is exhausted a low pressure region forms, causing cavitation on the inside surface of the elastomeric bladder. U.S. Pat. No. 5,410,978 discloses a flow-through EES aimed at preventing cavitation noise. A cylindrical elastomeric bladder is disposed within a bypass tube, open at one end. When the bladder is filled with fluid, the walls of the bladder contact the walls of the bypass tube at a sealing ring, sealing the system from the outside fluid atmosphere. When the fluid in the bladder is discharged, the bladder unseats from the bypass tube, allowing free flow of fluid from the outside fluid atmosphere toward the impulse fluid.
Another patent further illustrative of the art is U.S. Pat. No. 5,645,006 which discloses a bladder assembly for retaining fluid under pressure.
A primary disadvantage of prior art EES systems is the high level of elastic strain on the charged bladder resulting in unstable bladder geometry and reduced material cyclic life. A further disadvantage is the undesirable cavitation noise which can occur following launch. Another disadvantage is that large bladder volumes are required to ensure successful vehicle launch before a bladder is exhausted. Further, the prior art flow through EES also suffer from undesirable system complexity.